Thermally actuated electrical switch



c. w. BONDURANT 1,985,337

Dec. 25,1934.

THERMALLY ACTUATED ELECTRICAL SWITCH 5 Sheets-Sheet 2 Filed Feb. 12, 1931 1N1 'EIYTOR.

Car/ton W Bondurant 5M W w A TTORNE Y.

c. w. BONDURANT THERMALLY ACTUATED ELECTRICAL SWITCH Filed Feb. 12,

1951 's Sheets-Sheet s I N VEN TOR.

Car/ton 14/. Honduran! ATTORNEY.

Dec. 25, 1934.

Patented Dec. 25,

THERMALLY ACTUATED ELECTRICAL SWITCH Carlton Walter Bondurant, Cleveland, Ohio, as-= signer to The Bishop & Babcock Sales 60mpany, Cleveland, @hic, a corporation of Ohio Application February 212, 119311, Serial No. 515,262

28 Clai ($11. 200-3140) This invention relates to electrical switches and particularly to thermally actuated switches.

My invention is applicable to numerous uses but I have chosen to illustrate and describe it herein as embodied in a form of construction adaptable for use in connection with refrigerating apparatus to respectively stop and start the refrigerant compressor motor upon the attainment respectively of predetermined upper and lower temperatures in the refrigerator.

One of the objects of this invention is to provide an improved electrical switch of the snapaction type.

Another object is to provide an electric switch of the type adapted to move abruptly with an improved snap-action from open to closed position .and vice versa-at predetermined points in the range of movement of an operating element movable in alternate directions.

Another object is to provide such an electric switch having improved means for adjusting the relative position of the movable operating element at which the snap-action occurs.

Another object is to provide an electric switch of the type adapted to snap from open to closed position at predetermined points in the movement of a switch operating element and having improved means for adjustably varying the amount -of movement of the operating element to effect the snap-action.

Another object is to provide in a thermally actuated switch, adapted to open and close its contacts atpredetermined temperatures, an improved adjusting means for adjustably varying the upper and/or lower temperatures at which the switch operates. I

Another object is to provide in a thermally actuated switch, an improved adjusting means for varying the differential or difference of temperature degrees between the upper andfllower temperatures at which the electric switch operates.

Another object is to provide'in a thermally actuated switch, an improved adjusting means for adjustably varying the range or actual upper and lower temperatures at which the switch operates.

Another object is to provide a thermally actuated switch of the type referred to in which the said differential" and said range may be separately adjusted.

Another object is to provide in an electric switch of the class described, an improved means I for indicating the adjustments thereof.

Another object is to provide in a thermally actuated electric switch having an adjustment for varying the temperature at which it operates, an improved means for bringing the operating temperature into conformity with a. predetermined fixed indicating scale or index.

Another object is to provide an improved thermally actuated electric switch of the expansible fluid bulb and/or thermostatic bellows type.

Another object is to provide a thermostatic electric switch of improved construction which will be simple and cheap to construct and assemble, and simple and easy to adjust and eflicient and durable in operation.

Another object of my invention is to provide for an improved thermally operable electric switch mechanism adapted to be employed in connection with refrigerating mechanisms wherein the switch is provided with a common adjusting means which may be alternatively operated at will to adjust the degree of temperature provided by the refrigerating mechanism and/or to actuate the switch to cut out the refrigerating mechanism, so that defrosting be effected.

Other objects will be apparent to those skilled in the art to which my invention appertains.

My invention is fully disclosed in the followingdescription taken in connection .with the accompanying drawings, in which:

Fig. 1 is a longitudinal cross-sectional view of an embodiment of my invention;

Fig. 2 is a front elevational the embodiment of Fig. 1;

Fig. 3 is a top plan view taken from the plane 3 of Fig. l;

Fig. 4 is a view taken from the plane 4 of Fig. i, with parts behind the sectional plane omitted for simplicity;

Fig. 5 is a separate view, to a slightly enlarged scale, of switch parts shown in Fig. 1;

Fig. 6 is a view to a greatly enlarged scale, and somewhat diagrammatic, of a switch mechanism shown in Fig. 1;

Fig. '7 is a sectional view taken from the plane 7 of Fig. 6;

Fig. 8 is a view taken from the plane 8 of Fig. 7; v

Fig. e is a. partial cross-sectional view taken from the plane 901' Fig. 1;

Fig. 1c is an elevational view of another embodiment of my invention;

Fig. 11 is a cross-sectional view of the upper part of the embodiment of Fig. 10, taken from the plane 11 of that figure.

Fig. 121s a view otherwise like that of Fig. 1, but showing the electrical switch mechanism view of a part of erating and switch adjusting means. This figure is for the purpose of showing the reversibility of the electrical contact operating, mechanism.

Fig. 13 is a view otherwise like that of Fig. 2 but showing the intermediate switch casing in relatively inverted position.

Referring to the drawings, I have shown at 1 and 2, upper and lower switch housing portions preferably formed from molded insulating material such as bakelite and interiorly formed to provide a switch chamber 3, the portions 1 and 2 being in engagement with each other on a plane of contact 4. Above the housing portion 1 is a spring housing 5 having an outwardly extending annular flange 6 resting on the housing portion 1. Below the switch housing is a thermostat housing 7 provided with an outwardly directed annular flange 6 resting on the lower housing portion 2. By means of bolts 9 extending through suitable perforations in the flanges 8 and 6 and through suitable bores in the lateral portions or the housing portions 1 and 2, and by means of nuts 10 on the bolts 9, the tour housing members 1, 2, 5 and 7 are rigidly clamped and secured together.

In dotted lines at 113, 1 show clamping nuts, which are threaded onto the screws 9, these being embedded in the housing portion 2 for the switch mechanism and are provided so that when assembling the mechanism the housing portion 2 may be first securely mounted on the thermostat housing 7, to prevent undue longitudinal expansion of the interiorly disposed thermostat l? subsequently described under the normal ternperatures prevailing during the assembly of the mechanism. It will be understood from portions of the description pertaining thereto which tollows, that the tube 5 1 and thermostat 4'1 contain an expansible fluid mediu which at normal ambient temperatures would longitudinally ex pand the thermostat 4? beyond the flange 6 of the thermostat housing, and the additional nuts 113 are provided so that the switch housing por= tion 2 may be securely mounted onto the flange 8, before the rest of the switch adjusting mechanism is supplied to the assembly, and pref erably just before the tube 5 1 is supplied with the thermally expansible medium.

The chamber 3 has a ledge 11 upon which, and at opposite sides thereof is disposed a pair of resiliently yieldable stationary contacts 12-12 leading from which is a corresponding pair or conductors 13-13, Fig. 4, respectively connected by screws 1 1 to terminal elements 15-15, which are molded securely in the housing 2 having inner portions 16-16 secured by the screws 14 and outer portions 17-17 projecting from the housing portion 2, and being in the form of hooks whereby a terminal cap 19 provided with conducting wires 18 leading therelnto and provided internally with contact points not shown may be interlocked and secured to the housing portion 2 and with the contact points making electrical contact with the terminal elements 15-15. The construction of the cap 19 and its associated parts and the means of interlocking it with the housing portion 2 constitutes no essential part of my invention and may be of well known construction, the preferred form being one whereby the cap may be applied to the terminal elements 15 and rotated to lock it with the elements 15 and to make electrical contact therewith.

The housing portions 1 and 2 are provided re- Leases? spectively with bores axially aligned 26 and ,21 in which are mounted for axial reciprocation a pair of axially aligned stems 22 and 23 respectively.-

The stems 22 and 23 are preferably of circular cross-section. The stem 22 is provided with a shoulder 24 at a portion thereof disposed within the chamber 3, thus providing an axially extending shank 25 of reduced diameter, which extends into a suitable bore 26 in the confronting end 27 of the stem 23. The stems 22 and 23 are forceably held toward each other, and between the shoulder 2 and the end 2'1 thereof is clamped a set of switch elements which will now be described.

A pair of metal clamp plates 28 and 29, generally of lJ-shape in cross-section with the legs of the U widely divergent, embrace, respectively, the end 2'? and the shoulder 24 of the stems and have disposed therebetween a pivoting plate 30. The clamp plates 28 and 25 in plan view are generally rectangular as shown for the plate 28 in Fig; 5. The pivot plate 30 is preferably formed from flat metal and in plan view as shown in Fig. 5 is generally I-Shaped, thus providing therefor a body portion 31 and end portions 32 which extend laterally beyond the body portion 31, for a purpose to be described. The plates 28, 29 and 30 are rigidly riveted together by spaced pins 33-33 having shank portions 34-34 of reduced diame ter, providing shoulders 35-35, the shanks 3 1 being projected through suitable aligned perforations in the plates 28, 29 and 30, and riveted over at their ends 56-36 to clamp the said plates between the riveted ends and the shoulders 35. The pins 33 extend upwardly through perfora tions 37-37 in the housing portion 1 and thus guide the above described plate assembly, and as will later appear, associated switch parts, and prevent the rotation 01" the same around the central axis of the housing 1-2. The plates 26, 29 and 30 are also perforated along the central axis as at 38, and through the perforation the shanl; 25 of the stem 22 extends plate assembly is disposed symmetrically with respect to the stems 22 and 25, and secured against shifting laterally with respect to the stem 22 and 23.

A pair of switch arms 39-39 having contact points 40 riveted thereto are formed from flat sheet metal. @n portions of the arms spaced from the contact points 16, the arms are provided with rectilinear edges li- 11 which abut upon the body portion 31 01' the plate 36 and are substantially coextensive with the same and are therefore embraced and trapped by the projecting end portions 32-32 of the plate 36. Laterally the arms 39 are provided with ears 12-12 on opposite sides thereof, and a pair of tension springs 13 connect the ears 42 as shown in Fig. 5.

The edges 41-21 may be bevelled as shown in Fig. 6, to provide a ltnife edge construction for hinging of the arms 59 on the plate 25.

With the parts just described arranged as in Fig. 1 or as in Fig. 6, the switch arms 39 may have a hinging action from the solid line position to the dotted line position, Fig. 6, the springs 43 holding the arms inwardly against the edges of the plate 30. Also, a snap-action of the arms 39 is effected, the springs 43 engaging the arms 39 below the hinge plate 36 in the solid line position and above it in the dotted line position and snapping the plate from one position to the other in a manner well understood in the art.

With the parts illustrated as in Figs. 1 and 6, the contact points 20-46 are in contact with the stationary contacts 12. These stationary conwhereby the I breaking contact at tacts 12 are merely relatively stationary, since they are mounted on the ends of leaf spring con nectors 13, and being normally elevated some= what above the ledge 11 of the housing portion 2, are adapted to yield when engaged by the reciprocatory contacts to the end that a me chanical wiping contact is had which insures that the contacts are kept clean and good electrical connections secure.

Upon movement downwardly of the stems 22 and 23 by means to be described, the "hinge plate 30 will be depressed to a point where the springs 43 will rock the arms 39 to an upper position, 40-12, the upward move ment of the arms being stopped by the engagement 01' their outer ends upon adjustingnains 44-44. The cams 44 comprise body portions d5 generally cylindrical and disposed at opposite sides of the housing portions l and 2 and on a common axis and rotatable about the axis in suit= able confronting recesses of the housing portions 1 and 2, the common axis preferably coinciding with the contact plane 4 of the housing portion. To prevent endwise shifting of the body portions 45, they are provided with annular coaxial ribs 46-46 disposed in corresponding grooves in the housing portion 1 and 2. Inwardly oi the loody portions 45, extend the adjusting cams 44-44, the cams comprising eccentrically disposed cyl inders preferably formed integrally with the body portions 45.

The body portions are normally clamped be tween the housing portions 1 and 2, but may be released sufliciently to permit of turning them by loosening of the bolts 9.

Upon rotation of the body portions 45, the cams 44 will be depressed or elevated thereby. As shown in Fig. 6, the upward throw oi the arms 39, which is limited by engagement of the end oi the arms with the cylindrical surface of the cams 44, may be adjusted by adjusting the vertical position of the cams 44 by rotation of the body portions 45. Two upper positions for one oi the arms 39 is shown in Fig. 6'in illustration of this action.

By means of adjustment just described, the amount of upward movement of the stems 22 and 23 necessary to snap the switch arms 39 from their upper or open circuit position to their lower or contact-making position, may be adjustably varied. v

In the housing '7 is a thermostat 47 of the bellows type, having its lower axial end sealed as at 48 to a bore 49 'of the casing 7. Its upper end is sealed as at 50 to a sheet metal head 51. Into a suitable centrally disposed depression or cup, 52, a block 53 is pressed and into which block is seated the lower end of the stem 22. The interior of the bellows 47 communicates with a bulb 54 met erably formed from a piece of metal tubing, sealed at its upper endin a perforation in the housing bottom 49 and at its lower end provided with aninternally telescoped and sealed plug 55 threaded exteriorly oi the bulb as at 56, and provided with an axial duct 57 which duct may be sealed by a plug 58 and sealing material 59. The parts'just described for the bulb 54 are well known in the art and provide means for creating a desired vacuum within the bulb 54'and bellows 47 and for injecting into the bulb 54 a suitable amount of thermally expansible fluid and for sealing the same therein.

The housing 5 of generally cylindrical form and preferably made from sheet metal has rotat-= ably mounted in a perforation 64 in its upper end an internally threaded nut 60, the nut 60 being 3 restrained from axial movement by a flange 61 preferably formed from a separate piece of sheet metal secured to the nut and by a handle element 62 formed from sheet metal and provided with a perforation adapted to be forceably pressed over a cylindrical portion 63 of the nut 60. The flange 61 and handle 62, extending radially from the nut 66, overlap the peripheral edge of the perforation 64 in the upper end of the housing 5, and thus the nut 60 may be rotated on its axis by the handle element 62 but is prevented from axial movement by engagement of the flange 61 and handle element 62 with the end wall 65 oi the 7 housing 5.

The handle 62 has a serrated hole to engage with a correlativeiy indented portion of the nut 66, thereby making it possible to rotatively place the handle 62' in any desired position wherein it may be locked tightly in place by the nut 81.

Internally oi the nut 66 and meshed with the threads thereof is a screw 66 having on its lower inner end an annular flange 67 preferably formed from a separate piece of sheet metal and secured to the screw 66. As shown in Fig. 9, the flange 67 has a notch 66 in its periphery intermeshed with an inwardly projecting key 69 of the lions ing 5 formed by indenting the wall thereof. Thus when the nut 60 is rotated, the screw 66 is propelled axially but is prevented from rotation by the notch 68 and key 69.

The screw 66 is bored axially as at 76 and rotatably mounted in the bore is a cylindrical shank 71 having at its upper end a screwdriver slot 72 for turning it, and at its lower end enlarged in diameter to provide a shoulder 73 engaging the lower end of the screw 66, and a screw-threaded stud 74extending downwardly from the screw 66 coaxial therewith.

On the screw 74 is threaded a head '75 provided with an annular flange 76, abutting upwardly against which'is one end of a helical compression spring 77.

The stem 23 above described, projects upwardly out of the housing portion 1 and its upper end is seated in a 79 provided with an annular flange 80, upon which flange abuts the other end 01' the spring 77.

To install the switch device above described, his associated with a refrigerating apparatus in a manner to communicate temperature of the refrigerant to the bulb 54. The preferred mode of installation is to encircle the bulb 54 with a metal clamp not shown in the drawing, which clamp is mounted on a refrigerant-cooled portion of the refrigerating apparatus such, for example, as the condenser, and communicates by conduction, temperature of the refrigerant at that point to the bulb 54.

In the operation of the switch above described, assuming an initial adjustment which will be rei'erred to, if the temperature 01' the bulb 54 decreases due to operation of the refrigerator mechanism, the force of the spring 77 exerted downwardly on. the stem 23 and thenceto the stem 22 is transmitted to the expansible fluid in the bulb 54 and bellows 47 and collapses the bellows 47 in proportion to the amount of contraction or the fluid. Concurrently therewith, the stems 22 and23 move downwardly.

. It is to be understood that, as well known in the art, the refrigerating apparatus derives its power from an electric motor, the circuit to which is controlled by the contacts 40-12 of the switch herein under consideration. It, now, the above described downward movement of the stems 22 and are installed as a unit intermediate opposed flanges 6 and 8 of the housing parts and 7, and the switch operating means having like oppositely directed stems 22 and 23 projecting axially from the switch housing parts 1 and 2, that a mere reversal ofthe switch housing enables the switch operating and switch adjusting stems 22 and 23 to adopt alternative functions of the other.

Therefore, in the arrangement shown in Fig. 12, the bellows 47 through the stem 23 will supply pressure to the switch mechanism to open the.

switch contacts instead of closing them as in the arrangement of Fig. 1, and the operation of the switch is adjusted by pressure effects communicated through the spring 77 to the stem 22, which in the arrangement of Fig. 12 extends toward the spring 77 and engages the block 78 associated therewith.

My invention is not limited to the exact details of construction shown and described. Many modifications thereof and changes therein may be made within the scope of my invention without sacrificing its advantages.

I claim:

1. In a thermally actuable switch construction, a thermostat comprising an element movable responsive to temperature changes, a switch operable to be opened and closed by movement of the element at predetermined lower and upper temperatures, and adjustably movable means adapted to concurrently adjustably vary the responsiveness of said switch to efiect opening and closing operations thereof at higher or lower temperatures and adapted in an adjusted position to prevent closing of the switch, and means to adjustably vary the responsiveness of said switch to make it close at predetermined variable tem-: peratures, independently of the predetermined opening temperature, said last adjusting means comprising a stop for stopping movement of a movable element of the switch in its opening direction and adjustment means to variably position the stop.

2. In a thermally actuable switch construction, a thermostat comprising an element movable responsive to temperature changes, a switch operable to be opened and closed by movement of the element at predetermined lower and upper temperatures, and adjustably movable means adapted to concurrently adjustably vary the responsiveness of said switch to effect opening and closing operations thereof at higher or lower temperatures adapted in an adjusted position to positively prevent closing of the switch, and comprising a spring opposing movement of the movable element of the thermostat in other adjusted posi tions and means for adjusting the tension of the spring, and means to adjustably vary the responsiveness of said switch to make it close at predetermined variable temperatures, independently of the predetermined opening temperature comprising a stop for stopping movement of the movable element of the switch in opening direction and adjusting means to variably position the stop.

3. In a thermally actuable switch construction, a thermostat comprising an element movable responsive to temperature changes, a switch operable to be opened and closed by movement of the element at predetermined lower and upper v about a rotational axis stop eccentric to the axis engageable by the movtemperatures, and means to adjustably vary the responsiveness of said switch to make it close at predetermined variable temperatures, independently of the predetermined opening temperature, a stop for stopping movement of the movable element of the switch in opening direction, comprising a rotary element rotatably adjustable and an abutment on the able switch element.

4. In a thermally actuable switch construction, a thermostat comprising an element movable responsive to temperature changes, a switch operable to be opened and closed by movement of the element at predetermined lower and upper temperatures, and adjustment means adapted to concurrently adjustably vary the responsiveness of said switch to eiiect opening and closing operations thereof at higher and lower temperatures, said means comprising a spring opposing movement of the movable element, a screwthreaded element for varying the tension of the spring, and separate means for rotating the screw and for moving it bodily axially.

5. In a thermally actuable switch construction, a thermostat comprising an element movable responsive to temperature changes, a.

switch operable to be opened and closed by movement of the element at predetermined lower and upper temperatures, and adjustment means adapted to concurrently adjustably vary the responsiveness of said switch to effect opening and closing operations thereof at higher and lower temperatures, said means comprising a spring opposing movement of the movable element, a head engaging the spring, a screw element threaded in the head, means for rotating the screw element in the head, and means for moving the screw element bodily axially.

6. In a thermally actuable switch construction, a thermostat comprising an element movable responsive to temperature changes, a switch operable to be opened and closed by movement of the element at predetermined lower and upper temperatures, and adjustment means adapted to concurrently adjustably vary the responsiveness of said switch to eflect opening and closing operations thereof at higher and lower temperatures, said means comprising a spring opposing movement of the movable element, a screw-threaded element for varying the tension of the spring, and separate means for rotating the screw and for moving it bodily axially, said last-named means including a traveling screw element rotatably engaged by the screw-threaded element, an axially stationary nut threaded with the traveling screw element and a handle on the nut.

7. In a thermally actuable switch construction, a thermostat comprising an element movable responsive to temperature changes, a switch operable to be opened and closed by movement of the element at predetermined lower and upper temperatures, and adjustment means adapted to concurrently adjustably vary the responsiveness of said switch to efiect opening and closing operations thereof at higher and lower temperatures, said means comprising a spring opposing movement of the movable element, a screw-threaded element for varying the tension of the spring. and separate means for rotating the screw and for moving it bodily axially, said last-named means including a support rotatably engaged by the screw-threaded element, a cam follower on the support, a cam engaged with the follower, and a handle for adjustably moving the cam.

iii)

mechanism, a. thermostat comprising 8. In a thermally actuable switch construction, a switch housing, containing a switch mechanism, a thermostat housing, containing a thermostat mechanism, a spring housing, containing a thermostat opposing spring, the switch housing being. disposed between the spring and thermostat housings secured thereto and switch operable means connecting the spring and the thermostat to cause the switch to be closed at a predetermined high temperature and the thermostat housing and spring housing being interchangeable on the switch housing to optionally convert the switch construction from a thermostat closable to a thermostat openable switch construction.

9. In a thermally actuable switch construction, a switch housing, containing a switch mechanism, a thermostat housing, containing a thermostat, a spring housing, containing a thermostat opposing spring, the switch housing being disposed between the thermostat and spring housings, ccn= necting means extending through the switch housing and connecting the spring and the thermostat, and the switch being operable by movement of the connecting means to close upon at taininent oi a predetermined thermostat temperature, the thermostat housing and spring housing being interchangeable on the switch housing to optionally convert the switch construction from a thermostat closing to a thermostat opening switch construction.

it. In a thermally actuable switch construction, a walled switch housing, a switch enclosed in the switch housing, a pair of switch operating elements extending outwardly through perforations in opposite walls of the switch housing, a housing containing a switch operating thermostat connected to one element and a housing containing a thermostat opposing spring connected to the other element and the two housings interchangeably secured to opposite portions of the switch housing.

11in a thermally actuable electric switch mechanism, a switch housing, a snap-switch in the housing, a stern element connected to the switch mechanism and projecting through an aperture in the hous ng wall, a thermostat connected to the stem element externally oi the wall, a second stem element alimied with the first stem element projecting through an aperture in an other wall of the housing, and a thermostat op posing spring connected to the second stern element, the thermostat and connected stem element being interchangeable with the spring and connected second element and supported on the switch housing.

12. In a thermally actuable electric switch mechanism, the housing, a thermostat operable through a wall of the housing to operate the snap-switch in response to upper and lower temperatures of the thermostat, an adjustable stop comprising an element rotatably adjustably supported in a portion of the housing wall and having an eccentric portion projecting inwardly from the wall, for variably limiting the throw of the snap-switch to variably adjust the thermostat temperature at which the switch operates.

13. In a thermally actuable electric switch a movable element, a spring yieldingly opposing movement of the movable element, a pair of axially aligned stem elements connected respectively to the spring and to the movable element and having conironting portions, a switch construction disposed between the stem elements and comprising a head.

a switch housing, a snap-switch in ocales? clamped between the confronting portions of the stem elements, the head being provided with opposite laterally open parallel grooves, a switch arm in each groove abutting at one end upon the bottom. of the groove and extending outwardly from the groove and provided with a switch contact point on the other end of the arm, and a tension spring connecting the two arms.

14. in a thermostatically actuable electric snapswitch construction, a head provided with a pair of oppositely outwardly open grooves, a switch arm having an edge portion adapted to rock in each groove, a tension spring connecting spaced portions of the switch arm, a pair of stationary contacts adapted to stop movement of the arms in one direction, a pair of stops adapted to stop movement of the arms in the other direction, whereby movement of the head in alternate directions may cause the spring to snap the arms from contact-engaging closed position to stop-engaging open position and vice versa, and means for adjustably varying the position of the stops to vary the throw of the arms in open direction to vary the temperature at which the switch closes.

15. In a thermally actuable switch construction, a walled switch chamber, a switch mechanism in the chamber comprising a head provided with a pair of oppositely outwardly open grooves, a switch arm having a knife edge portion adapted to rock in each groove, a tension spring connecting spaced portions of the arms, a pair of stationary contacts adapted to stop movement or" the arms in one direction, a pair of stops adapted to stop movement of the arms in the other direction, whereby movement of the head in alternate directions may cause the arms to snap from switchopen to switch-closed position and vice versa, a pair of stem elements connected to the head and extending therefrom in opposite directions outwardly through perforations in the switch chamber, a thermostat comprising an element movable responsive to temperature changes connected to one stem element, and a thermostat opposing spring connected to the other stem element.

16. In a thermally actuable switch construction, a walled switch chamber, a switch mechanism in the chamber comprising a head provided with a pair of oppositely outwardly open grooves, a switch arm having a knife edge portion adapted to rocl: in each groove, a tension spring connecting spaced portions of the arms, a pair of stationary contacts adapted to stop movement of the arms in one direction, a pair of stops adapted to stop movement of the arms in the other direction, whereby movement of the head in alternate directions may cause the arms to snap from switch-open to switch-closed position and vice versa, a pair of stem elements connected to the head and extending therefrom in opposite directions outwardly through perforations in opposite walls of the switch chamber, a thermostat comprising an element movable responsive to tern perature changes connected. to one stem element, a thermostat opposing spring connected to the other stem element, a pair of housings enclosing the spring and the thermostat respectively and joined to the outer walls of the switch chamber 17. In a fluid pressure actuable electric switcl mechanism, a switch housing, a snap-switch it the housing, a stem element connected to 13114 switch mechanism and projecting through a1 aperture in the housing wall, a fluid pressure re sponsive element connected to the stem elemcn opposite walls of externally of the wall, a second stem element aligned with the first stem element projecting through an aperture in another wall of the hous ing, and an opposing spring to restrain movement of the second stem element.

18. In a thermally actuable switch construction, a thermostat comprising an element'movable responsive to temperature "changes, a switch operable to be opened and closed by movement of the element at predetermined lower and upper temperatures, and adjustment means to concurrently adjustably vary the responsiveness of said switch to effect opening and closing operations thereof at higher or lower temperatures, and adjustable to prevent closing of the switch at all temperatures.

19. A thermally actuable switch construction as described in claim 26 and in which the switch is preventedfrom closing at all temperatures by a switch movement blocking means rendered eifective by an adjustment of the adjustment means.

20. A thermally actuable switch construction as described in claim 26 and in which the adjustment means comprises an element adjustably movable thereby into a position to prevent closing of the switch at all temperatures.

21. A thermally actuable switch construction as described in claim 26 and in which the switch comprises an element movable upon movement of the switch toward closed position, and the adjustment means comprises an element movable to a position of adjustment, to prevent movement of the switch movable element to prevent closure of the switch at all temperatures.

22. In a thermally actuable switch construction, a thermostat comprising an element movable responsive to temperature changes, a switch operable to be opened and closed by movement of the element at predetermined lower and upper temperatures, means to adjustably vary the responsiveness of the switch to cause it to close at variable predetermined temperatures, the adjusting means comprising an adjustably rotatable element, and a stop associated with the retary element, movable, upon rotation of the rotatable element, relatively toward or from a movable portion of the switch and a predeter mined rotated position in one direction of rotation disposed to prevent operation of the switch.

23. In a thermally actuable switch construction, a thermostat comprising an element movable responsive to temperature changes, a switch operable to be opened and closed by movement of the element at predetermined lower and upper temperatures, and adjustment means adapted to concurrently adjustably vary the responsivenessof said switch to effect opening and closing operations thereof at higheror lower temperatures, said means comprising a spring, opposing movement of the movable element, a screw-threaded element for varying the tension of the spring and separate means for rotating the screw and for moving it bodily axially, said last-named means including a support rotatably engaged by the screw-threaded element, a rotary operable element, and a connection between the rotary operable element and the support for moving the support upon rotation of the operable element.-

24. In a switch mechanism adapted to be operated by a thermostat in response to changes of aemperature thereof, a snap switch comprising a novable switch element and resilient means to map it in alternate directions, a switch housing, a

contact and an abutment in the housing engageable respectively by snap movement of the snap switch movable element upon snap movement in alternate directions, the abutment comprising a cylindrical body portion oscillatablein the wall of the housing and anchored against longitudinal movement therein and having an abutment cam surface on one axial end oscillatably adjusts ably movable toward and from the switch movable element upon oscillation of the oscillatable element and having the outer axial end accessible exteriorly of the housing-and .the cam sur-. face being engageable by the snap switch movable element in one direction of movement.

25. In a switch mechanism adapted to be operated by a thermostat in response to changes of temperature thereof, a snap switch comprising a movable switch element and resilient means to snap it in alternate directions, a switch housing, a contact and an abutment in the housing engageable respectively by the snap switch movable element upon snap movement in alternate directions, the abutment comprising an oscillatable portion oscillatably adjustably movable toward and from the switch movable element upon oscillation of the oscillatable element and the cam surface being engageable by the snap switch movable element in one direction of snap movement, the switch housing being in two parts comprising respectively confronting cavities and peripherally mutually engageable to provide a switch enclosing housing, and the engageable peripheral portions being provided with corresponding notches in which is rotatively oscillatably mounted a generally cylindrical abutment portionaccessible at one end exteriorly of the housing to adjustably rotate it and provided interiorly with said oscillatable portion and cam surface, and means to clamp the two parts of the housing'together to irictionally engage the abutment body portion to prevent unintended rotation thereof.

26. In a thermally actuable switch construction, a thermostat comprising an element movable responsive to temperature changes, a switch operable to be opened and closed by movement of the element at predetermined lower and upper temperatures, and adjustment means adapted to concurrently adjustably vary the responsiveness of said switch to effect opening and closing operations thereof at higher or lower temperatures, said means comprising a spring, opposing movement of the movable element, a first adjusting vary the tension of the spring, a second adjustable element adjustably movable over a predetermined range of movement corresponding to different temperatures to adjustably vary the position of the first adjustable spondingly vary the tension of by movement of the first adjustable element may adjustably vary the adjustment effect of the sec-= 0nd adjustable element to adjustably vary the predetermined range of temperature.

27. In a thermally actuable switch construction, a thermostat comprising an element movable responsive to temperature changes, a switch operable to be opened and closed bymovement of the element at predetermined lower and upper temperatures, and adjustment means to adjustably vary the responsiveness of said switch to concurrently elfect opening and closing operations thereof at higher or lower temperatures, a movable element movable by movement of the temperature adjustment means to a positionto element to correelement adjustably movable to the spring where- 28. In e switch construction, a switch housing comprising two housing portions lieving con fronting cavities and peripheral portions mu= -txielly engageable to i'orm are enclosed chamber,

a switch assembly comprising a stem construm tion and movable snap switch elements mounted thereon, the stem construction comprising stem elements extending in opposite directions from the snap switch elements, the two housing pow tions being provided with opposite ciiemirer wall memos? perforations end the stem elements adopted to ice telescopecl through the perforations, means to secure the housing portions together in mutual peripheral engagement to enclose tire switch elements in the chamber and with the stem elements projecting outwardly therefrom, and the two housing portions adapted to support respectively a. thermostatic switch operating device and a switch movement opposing resilient device, one

stem element being engegeoiile Toy one device and the other stem element by the other device and the thermostatic switch operating device and the switch movement opposing device losing irrterciiorieeolole on time two housing; portions.

CARLTUN WALTER BQNDURANT. l1 

